1. Field of Invention
The present invention relates to a method of separating a thin film device, a method of transferring a thin film device, a thin film device, an active matrix substrate and a liquid crystal display device.
2. Description of Related Art
For example, the production of a liquid crystal display using a thin film transistor (TFT) is carried out through the step of forming the thin film transistor on a substrate by CVD or the like. The step of forming the thin film transistor on the substrate is accompanied by high-temperature treatment, and it is thus necessary to use a substrate made of a material having excellent heat resistance, i.e., high softening point and melting point. Therefore, at present, quartz glass is used as a substrate which can resist a temperature of about 1000° C., and heat-resistant glass is used as a substrate which can resist a temperature of about 500° C.
As described above, the substrate on which the thin film is mounted must satisfy conditions for producing the thin film device. Namely, the substrate used is determined to necessarily satisfy conditions for producing the device mounted thereon.
However, in consideration of only steps after completion of the substrate on which the thin film device such as TFT is mounted, the above-described substrate is not necessarily preferred.
For example, in cases in which the substrate is passed through the production process accompanied with high-temperature treatment, as described above, a quartz substrate, a heat-resistant glass substrate, or the like is used. However, such a substrate is very expensive, and thus causes an increase in product cost.
A glass substrate also has the property that it is heavy and brittle. In a liquid crystal display used for a portable electronic device such as a palm top computer, a portable telephone, or the like, a substrate is preferably as inexpensive as possible, lightweight, resistant to deformation, and hard to break even by dropping. However, in fact, the glass substrate is heavy and weak against deformation, and has the possibility of breakage by dropping.
Namely, there is a gap between the limits caused by production conditions and the preferable characteristics required for products, thereby causing great difficulties in satisfying both the conditions and characteristics.